Tee-nut fastening devices are widely used in many industries, in particular in the furniture industry. They consist of a sheet metal member having a sleeve with internal threads, and flanges around one end of the sleeve and spikes formed at right angles to the flanges which are embedded in the workpiece around a pre-drilled hole.
They are widely used for constructing furniture items such as bookshelves, cupboards, chairs, beds and the like, and in many other situations. Various forms of high-speed insertion machines have been devised, by means of which the Tee-nuts may be driven into a workpiece. Usually there is a pre-drilled hole in which the sleeve is received, and the flange lies on the surface of the workpiece with the spikes embedded in it, thereby holding the entire Tee-nut in position. Modified forms of Tee-nuts are available which are flared out at the free ends of the sleeves so as to provide a more secure hold in the workpiece. Other forms of Tee-nuts are available which are formed with sleeves capable of punching their own hole through the workpiece.
The rapidity and repetition rate of the insertion of such Tee-nuts into a workpiece is a significant cost factor in the production of the end product. In the past, insertion machines have been provided with hoppers. The Tee-nuts were simply dumped loose in the hopper, and the hopper vibrated, to separate the Tee-nuts and cause them to enter a feedslide. The feedslide supplied the Tee-nuts, one after another, to the punch.
These systems were not always reliable and in some cases the hoppers became jammed with Tee-nuts and in other cases the feedslide became jammed because the Tee-nuts would not slide down the feedslide.
Various examples of such Tee-nut setting machines are shown, one example being shown for example in U.S. Pat. No. 3,460,217. A modified form of Tee-nut machine in which the Tee-nuts were driven upwardly into the workpiece is shown in U.S. Pat. No. 4,821,940. The problem with these systems involving loose Tee-nuts is that the slide would feed the Tee-nuts to a feed mechanism which would then deliver them one at a time to a plunger or punch. This was relatively complex and costly, and was not always reliable, at the speeds of operation which are required.
With a view to overcoming many of these disadvantages and with a view to providing a much simpler machine, a Tee-nut inserting machine was devised, for receiving Tee-nuts from a coil or roll. The Tee-nuts themselves were formed into a coil by means of a backing tape or membrane, or in some cases by means of welded wire filaments. Examples of such systems are shown in U.S. Pat. Nos. 4,214,843; 5,327,645; 5,299,686 and 5,214,843.
The machines and Tee-nut strips disclosed in these patents overcame the problems arising from placing loose Tee-nuts in a hopper, and then attempting to sort out the Tee-nuts and feed them one by one down a Tee-nut slide.
However, the formation of the Tee-nuts into a strip by means of a flexible membrane such as a tape was not always totally satisfactory. In some cases, the membrane, which might be for example, paper or the like, would simply break between the Tee-nuts. In other cases, the formation of the Tee-nut strips by means of welded wires was not always satisfactory due to the difficulties and complexities of forming high-speed spot welds. In both systems, when the insertion machines were operated at high speed there was a tendency for the Tee-nut strips to become broken or Tee-nuts to become separated from the strip. In both cases this would lead to a false insertion of a Tee-nut, i.e. there would be a hole in the workpiece with no Tee-nut, and this was unacceptable.
The first objective of the invention therefore is to provide an improved fastener strip such as a Tee-nut strip which is capable of high-speed operation with fastener insertion machines, whether of the type described or otherwise.
A further requirement which has developed more recently, is the provision of a portable fastener applicator for example for use with Tee-nuts, similar to the air pressure-operated nailing applicators which are in common use.
A portable hand-held fastener applicator would have many advantages over the stand-alone applicator machines. However, in order to operate, a satisfactory form of fastener strip must be provided for the portable hand-held fastener applicator.